1. Field of the Invention
The present invention relates to a solar panel that is used in a pointer-type timepiece such as a wristwatch or a pointer-type measuring instrument such as a meter, and a timepiece including the solar panel.
2. Description of the Related Art
For example, a solar panel for use in a wristwatch is known in which a plurality of solar cells each formed into a fan shape so as to have an equal area are circularly arranged and connected in series, as described in Japanese Patent Application Laid-Open (Kokai) Publication No. 10-039057.
This type of solar panel is structured to have a through hole provided in its center and a pointer shaft inserted in the through hole to protrude upward. On the upper end of the pointer shaft, a pointer is mounted, and moves above the plurality of solar cells.
In this type of solar panel, the value of output current obtained by the plurality of solar cells as a whole becomes equal to the value of the smallest output current obtained by one of the plurality of solar cells due to electrical characteristics of a diode or the like.
Accordingly, when the pointer is positioned over one of the plurality of solar cells, the light-receiving area of the solar cell over which the pointer has been positioned becomes smaller than the light-receiving areas of the other solar cells.
As a result, the output current of the solar cell over which the pointer has been positioned becomes smaller than the output currents of the other solar cells, and the value of the output current obtained by the plurality of solar cells as a whole becomes equal to this smallest output current of the solar cell. Thus, there is a problem in this solar panel in that a loss of the output current of the plurality of solar cells as a whole is disadvantageously large.